During pregnancy, a balanced diet is essential to provide the energy and nutrients necessary to maintain the mothers health and allow the fetus to grow and develop in favorable conditions. In the United States, the importance of a balanced diet during pregnancy is highlighted by the large number of national and population-based nutrition monitoring surveys conducted to assess nutrient and supplement intake among pregnant and lactating women. Despite this research, the impact of imbalances in maternal diet on adverse pregnancy outcomes, especially in adequately nourished populations, remains a matter of debate. Of particular note, the studies to date that have assessed the influence of maternal nutrition on pregnancy outcomes typically limited the data collection to a single assessment among small samples that lack racial/ethnic or socio-economic heterogeneity. We propose to address all of these significant limitations in the existing literature by conducting a multi-center, prospective study involving a racially/ethnically diverse sample. The data collection, in turn, will involve multiple measurements, in order to determine: (1) nutrient and supplement (including herbal supplements) intake during the pre- and peri-conceptional period, as well as the pregnancy, and (2) the association between meal patterns, macro- and micronutrients, and dietary supplements and pregnancy complications (gestational diabetes, preeclampsia) and outcomes (fetal growth, birthweight, preterm birth). In addition, we will validate the web-based Automated Self-Administered 24-hour Recall used during the second and third trimesters. This data collection will be accomplished via an addition to the prospective study entitled The National Standard for Normal Fetal Growth. The plan of this study is to recruit approximately 3,000 women (2,400 healthy non-obese women and 600 obese women), between 18 and 34 years of age, with an in utero singleton pregnancy at less than 13 weeks of gestation. Each woman will then be followed through the course of their pregnancy. The sample will be divided equally among four self-identified race/ethnicity groups: non-Hispanic White, African-American, Hispanic, and Asian/Pacific. At enrollment, the study participants will be asked to complete a self-administered Food Frequency Questionnaire (the National Cancer Institutes Diet History Questionnaire) to assess maternal diet both prior to pregnancy and during the first trimester. In addition, the participants will be required to complete four web-based Automated Self-Administered 24-hour Recalls (ASA-24) during the course of their pregnancy twice during the second trimester and twice again during the third trimester. The information from the modified NCI-DHQ will be used to determine nutrient and supplement intake during the pre- and periconceptional period, whereas data from the ASA-24 will be used to describe meal patterns during the course of the pregnancy and to examine intra-individual variability in dietary intake.